Mounting arrangement for light emitting diodes

ABSTRACT

A modular light emitting diode (LED) mounting configuration is provided including a light source module having a plurality of pre-packaged LEDs arranged in a serial array. The module includes a heat conductive body portion adapted to conduct heat generated by the LEDs to an adjacent heat sink. As a result, the LEDs are able to be operated with a higher current than normally allowed. Thus, brightness and performance of the LEDs is increased without decreasing the life expectancy of the LEDs. The LED modules can be used in a variety of illumination applications employing one or more modules.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/789,357, which was filed on Feb. 27, 2004, now U.S. Pat. No.7,114,831, which is a continuation of U.S. application Ser. No.09/693,548, which was filed on Oct. 19, 2000, now U.S. Pat. No.6,712,486, which claims the benefit of U.S. Provisional PatentApplication Nos. 60/160,480, which was filed on Oct. 19, 1999 and60/200,531, which was filed on Apr. 27, 2000. The entirety of each ofthese related applications is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is in the field of light emitting diode (LED)lighting devices and more particularly in the field of an LED lightingmodule having heat transfer properties that improve the efficiency andperformance of LEDs.

2. Description of the Related Art

Light emitting diodes (LEDs) are currently used for a variety ofapplications. The compactness, efficiency and long life of LEDs isparticularly desirable and makes LEDs well suited for many applications.However, a limitation of LEDs is that they typically cannot maintain along-term brightness that is acceptable for middle to large-scaleillumination applications. Instead, more traditional incandescent orgas-filled light bulbs are often used.

An increase of the electrical current supplied to an LED generallyincreases the brightness of the light emitted by the LED. However,increased current also increases the junction temperature of the LED.Increased juncture temperature may reduce the efficiency and thelifetime of the LED. For example, it has been noted that for every 10°C. increase in temperature, silicone and gallium arsenide lifetime dropsby a factor of 2.5 –3. LEDs are often constructed of semiconductormaterials that share many similar properties with silicone and galliumarsenide.

SUMMARY OF THE INVENTION

Accordingly, there is a need in the art for an LED lighting apparatushaving heat removal properties that allow an LED on the apparatus tooperate at relatively high current levels without increasing thejuncture temperature of the LED beyond desired levels.

In accordance with an aspect of the present invention, an LED module isprovided for mounting on a heat conducting surface that is substantiallylarger than the module. The module comprises a plurality of LED packagesand a circuit board. Each LED package has an LED and at least one lead.The circuit board comprises a thin dielectric sheet and a plurality ofelectrically-conductive contacts on a first side of the dielectricsheet. Each of the contacts is configured to mount a lead of an LEDpackage such that the LEDs are connected in series. A heat conductiveplate is disposed on a second side of the dielectric sheet. The platehas a first side which is in thermal communication with the contactsthrough the dielectric sheet. The first side of the plate has a surfacearea substantially larger than a contact area between the contacts andthe dielectric sheet. The plate has a second side adapted to providethermal contact with the heat conducting surface. In this manner, heatis transferred from the module to the heat conducting surface.

In accordance with another aspect of the present invention, a modularlighting apparatus is provided for conducting heat away from a lightsource of the apparatus. The apparatus comprises a plurality of LEDs anda circuit board. The circuit board has a main body and a plurality ofelectrically conductive contacts. Each of the LEDs electricallycommunicates with at least one of the contacts in a manner so that theLEDs are configured in a series array. Each of the LEDs electricallycommunicates with corresponding contacts at an attachment area definedon each contact. An overall surface of the contact is substantiallylarger than the attachment area. The plurality of contacts are arrangedadjacent a first side of the main body and are in thermal communicationwith the first side of the main body. The main body electricallyinsulates the plurality of contacts relative to one another.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described herein above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught herein without necessarilyachieving other objects or advantages as may be taught or suggestedherein.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments of the presentinvention will become readily apparent to those skilled in the art fromthe following detailed description of the preferred embodiments havingreference to the attached figures, the invention not being limited toany particular preferred embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an LED module having features inaccordance with the present invention.

FIG. 2 is a schematic side view of a typical pre-packaged LED lamp.

FIG. 3 is a top plan view of the LED module of FIG. 1.

FIG. 4 is a side plan view of the apparatus of FIG. 3.

FIG. 5 is a close-up side view of the apparatus of FIG. 3 mounted on aheat conductive member.

FIG. 6 is another sectional side view of the apparatus of FIG. 3 mountedonto a heat conductive flat surface.

FIG. 7 is a side plan view of an LED module having features inaccordance with another embodiment of the present invention.

FIG. 8 is a side plan view of another LED module having features inaccordance with yet another embodiment of the present invention.

FIG. 9 is a perspective view of an illumination apparatus havingfeatures in accordance with the present invention.

FIG. 10 is a side view of the apparatus of FIG. 9.

FIG. 11 is a bottom view of the apparatus of FIG. 9.

FIG. 12 is a top view of the apparatus of FIG. 9.

FIG. 13 is a schematic view of the apparatus of FIG. 9 mounted on atheater seat row end.

FIG. 14 is a side view of the apparatus of FIG. 13 showing the mountingorientation.

FIG. 15 is a side view of a mounting barb.

FIG. 16 is a front plan view of the illumination apparatus of FIG. 9.

FIG. 17 is a cutaway side plan view of the apparatus of FIG. 20.

FIG. 18 is a schematic plan view of a heat sink base plate.

FIG. 19 is a close-up side sectional view of an LED module mounted on amount tab of a base plate.

FIG. 20 is a plan view of a lens for use with the apparatus of FIG. 9.

FIG. 21 is a perspective view of a channel illumination apparatusincorporating LED modules having features in accordance with the presentinvention.

FIG. 22 is a close-up side view of an LED module mounted on a mount tab.

FIG. 23 is a partial view of a wall of the apparatus of FIG. 21, takenalong line 23—23.

FIG. 24 is a top view of an LED module mounted to a wall of theapparatus of FIG. 21.

FIG. 25 is a top view of an alternative embodiment of an LED modulemounted to a wall of the apparatus of FIG. 21.

FIG. 26A is a side view of an alternative embodiment of a lightingmodule being mounted onto a channel illumination apparatus wall member.

FIG. 26B shows the apparatus of the arrangement of FIG. 26A with thelighting module installed.

FIG. 26C shows the arrangement of FIG. 26B with a lens installed on thewall member.

FIG. 26D shows a side view of an alternative embodiment of a lightingmodule installed on a channel illumination apparatus wall member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference first to FIG. 1, an embodiment of a light-emitting diode(LED) lighting module 30 is disclosed. In the illustrated embodiment,the LED module 30 includes five pre-packaged LEDs 32 arranged on oneside of the module 30. It is to be understood, however, that LED moduleshaving features in accordance with the present invention can beconstructed having any number of LEDs 32 mounted in any desiredconfiguration.

With next reference to FIG. 2, a typical pre-packaged LED 32 includes adiode chip 34 encased within a resin body 36. The body 36 typically hasa focusing lens portion 38. A negative lead 40 connects to an anode side42 of the diode chip 34 and a positive lead 44 connects to a cathodeside 46 of the diode chip 34. The positive lead 44 preferably includes areflector portion 48 to help direct light from the diode 34 to the lensportion 38.

With next reference to FIGS. 1–5, the LED module 30 preferably comprisesthe five pre-packaged LED lamps 32 mounted in a linear array on acircuit board 50 and electrically connected in series. The illustratedembodiment employs pre-packaged aluminum indium gallium phosphide(AlInGaP) LED lamps 32 such as model HLMT-PL00, which is available fromHewlett Packard. In the illustrated embodiment, each of the pre-packagedLEDs is substantially identical so that they emit the same color oflight. It is to be understood, however, that nonidentical LEDs may beused to achieve certain desired lighting effects.

The illustrated circuit board 50 preferably is about 0.05 inches thick,1 inch long and 0.5 inch wide. It includes three layers: a coppercontact layer 52, an epoxy dielectric layer 54 and an aluminum main bodylayer 56. The copper contact layer 52 is made up of a series of sixelongate and generally parallel flat copper plates 60 that are adaptedto attach to the leads 40, 44 of the LEDs 32. Each of the coppercontacts 60 is electrically insulated from the other copper contacts 60by the dielectric layer 54. Preferably, the copper contacts 60 aresubstantially coplanar.

The pre-packaged LEDs 32 are attached to one side of the circuit board50, with the body portion 36 of each LED generally abutting a side ofthe circuit board 50. The LED lens portion 38 is thus pointed outwardlyso as to direct light in a direction substantially coplanar with thecircuit board 50. The LED leads 40, 44 are soldered onto the contacts 60in order to create a series array of LEDs. Excess material from theleads of the individual pre-packaged LED lamps may be removed, ifdesired. Each of the contacts 60, except for the first and last contact62, 64, have both a negative lead 40 and a positive lead 44 attachedthereto. One of the first and last contacts 62, 64 has only a negativelead 40 attached thereto; the other has only a positive lead 44 attachedthereto.

A bonding area of the contacts accommodates the leads 40, 44, which arepreferably bonded to the contact 60 with solder 68; however, eachcontact 60 preferably has a surface area much larger than is requiredfor adequate bonding in the bonding area 66. The enlarged contactsurface area allows each contact 60 to operate as a heat sink,efficiently absorbing heat from the LED leads 40, 44. To maximize thisrole, the contacts 60 are shaped to be as large as possible while stillfitting upon the circuit board 50.

The dielectric layer 54 preferably has strong electrical insulationproperties but also relatively high heat conductance properties. In theillustrated embodiment, the layer 54 is preferably as thin aspracticable. For example in the illustrated embodiment, the dielectriclayer 54 comprises a layer of Thermagon® epoxy about 0.002 inches thick.

It is to be understood that various materials and thicknesses can beused for the dielectric layer 54. Generally, the lower the thermalconductivity of the material used for the dielectric layer, the thinnerthat dielectric layer should be in order to maximize heat transferproperties of the module. For example, in the illustrated embodiment,the layer of epoxy is very thin. Certain ceramic materials, such asberyllium oxide and aluminum nitride, are electrically non-conductivebut highly thermally conductive. When the dielectric layer isconstructed of such materials, it is not as crucial for the dielectriclayer to be so very thin, because of the high thermal conductivity ofthe material.

In the illustrated embodiment, the main body 56 makes up the bulk of thethickness of the circuit board 50 and preferably comprises a flataluminum plate. As with each of the individual contacts 60, the mainbody 56 functions as a heat conduit, absorbing heat from the contacts 60through the dielectric layer 54 to conduct heat away from the LEDs 32.However, rather than just absorbing heat from a single LED 32, the mainbody 56 acts as a common heat conduit, absorbing heat from all of thecontacts 60. As such, in the illustrated embodiment, the surface area ofthe main body 56 is about the same as the combined surface area of allof the individual contacts 60. The main body 56 can be significantlylarger than shown in the illustrated embodiment, but its relativelycompact shape is preferable in order to increase versatility whenmounting the light module 30. Additionally, the main body 56 isrelatively rigid and provides structural support for the lighting module30.

In the illustrated embodiment, aluminum has been chosen for its highthermal conductance properties and ease of manufacture. It is to beunderstood, however, that any material having advantageous thermalconductance properties, such as having thermal conductivity greater thanabout 100 watts per meter per Kelvin (W/m-K), would be acceptable.

A pair of holes 70 are preferably formed through the circuit board 50and are adapted to accommodate a pair of aluminum pop rivets 72. The poprivets 72 hold the circuit board 50 securely onto a heat conductivemount member 76. The mount member 76 functions as or communicates with aheat sink. Thus, heat from the LEDs 32 is conducted with relativelylittle resistance through the module 30 to the attached heat sink 76 sothat the junction temperature of the diode chip 34 within the LED 32does not exceed a maximum desired level.

With reference again to FIGS. 3 and 5, a power supply wire 78 isattached across the first and last contacts 62, 64 of the circuit board50 so that electrical current is provided to the series-connected LEDs32. The power supply is preferably a 12-volt system and may be AC, DC orany other suitable power supply. A 12-volt AC system may be fullyrectified.

The small size of the LED module 30 provides versatility so that modulescan be mounted at various places and in various configurations. Forinstance, some applications will include only a single module for aparticular lighting application, while other lighting applications willemploy a plurality of modules electrically connected in parallelrelative to each other.

It is also to be understood that any number of LEDs can be included inone module. For example, some modules may use two LEDs, while othermodules may use 10 or more LEDs. One manner of determining the number ofLEDs to include in a single module is to first determine the desiredoperating voltage of a single LED of the module and also the voltage ofthe power supply. The number of LEDs desired for the module is thenroughly equal to the voltage of the power supply divided by theoperating voltage of each of the LEDs.

The present invention rapidly conducts heat away from the diode chip 34of each LED 32 so as to permit the LEDs 32 to be operated in regimesthat exceed normal operating parameters of the pre-packaged LEDs 32. Inparticular, the heat sinks allow the LED circuit to be driven in acontinuous, non-pulsed manner at a higher long-term electrical currentthan is possible for typical LED mounting configurations. This operatingcurrent is substantially greater than manufacturer-recommended maximums.The optical emission of the LEDs at the higher current is also markedlygreater than at manufacturer-suggested maximum currents.

The heat transfer arrangement of the LED modules 30 is especiallyadvantageous for pre-packaged LEDs 32 having relatively small packagingand for single-diode LED lamps. For instance, the HLMT-PL00 model LEDlamps used in the illustrated embodiment employ only a single diode, butsince heat can be drawn efficiently from that single diode through theleads and circuit board and into the heat sink, the diode can be run ata higher current than such LEDs are traditionally operated. At such acurrent, the single-diode LED shines brighter than LED lamps that employtwo or more diodes and which are brighter than a single-diode lampduring traditional operation. Of course, pre-packaged LED lamps havingmultiple diodes can also be employed with the present invention. It isalso to be understood that the relatively small packaging of the modelHLMT-PL00 lamps aids in heat transfer by allowing the heat sink to beattached to the leads closer to the diode chip.

With next reference to FIG. 5, a first reflective layer 80 is preferablyattached immediately on top of the contacts 60 of the circuit board 50and is held in position by the rivets 72. The first reflector 80preferably extends outwardly beyond the LEDs 32. The reflective materialpreferably comprises an electrically non-conductive film such as visiblemirror film available from 3M. A second reflective layer 82 ispreferably attached to the mount member 76 at a point immediatelyadjacent the LED lamps 32. The second strip 82 is preferably bonded tothe mount surface 76 using adhesive in a manner known in the art.

With reference also to FIG. 6, the first reflective strip 80 ispreferably bent so as to form a convex reflective trough about the LEDs32. The convex trough is adapted to direct light rays emitted by theLEDs 32 outward with a minimum of reflections between the reflectorstrips 80, 82. Additionally, light from the LEDs is limited to beingdirected in a specified general direction by the reflecting films 80,82. As also shown in FIG. 6, the circuit board 50 can be mounteddirectly to any mount surface 76.

In another embodiment, the aluminum main body portion 56 may be ofreduced thickness or may be formed of a softer metal so that the module30 can be partially deformed by a user. In this manner, the module 30can be adjusted to fit onto various surfaces, whether they are flat orcurved. By being able to adjust the fit of the module to the surface,the shared contact surface between the main body and the adjacent heatsink is maximized, improving heat transfer properties. Additionalembodiments can use fasteners other than rivets to hold the module intoplace on the mount surface/heat sink material. These additionalfasteners can include any known fastening means such as welding, heatconductive adhesives, and the like.

As discussed above, a number of materials may be used for the circuitboard portion of the LED module. With specific reference to FIG. 7,another embodiment of an LED module 86 comprises a series of elongate,flat contacts 88 similar to those described above with reference to FIG.3. The contacts 88 are mounted directly onto the main body portion 89.The main body 89 comprises a rigid, substantially flat ceramic plate.The ceramic plate makes up the bulk of the circuit board and providesstructural support for the contacts 88. Also, the ceramic plate has asurface area about the same as the combined surface area of thecontacts. In this manner, the plate is large enough to providestructural support for the contacts 88 and conduct heat away from eachof the contacts 88, but is small enough to allow the module 86 to berelatively small and easy to work with. The ceramic plate 89 ispreferably electrically non-conductive but has high heat conductivity.Thus, the contacts 88 are electrically insulated relative to each other,but heat from the contacts 88 is readily transferred to the ceramicplate 89 and into an adjoining heat sink.

With next reference to FIG. 8, another embodiment of an LED lightingmodule 90 is shown. The LED module 90 comprises a circuit board 92having features substantially similar to the circuit board 50 describedabove with reference to FIG. 3. The diode portion 94 of the LED 96 ismounted substantially directly onto the contacts 60 of the lightingmodule 90. In this manner, any thermal resistance from leads ofpre-packaged LEDs is eliminated by transferring heat directly from thediode 94 onto each heat sink contact 60, from which the heat isconducted to the main body 56 and then out of the module 90. In thisconfiguration, heat transfer properties are yet further improved.

As discussed above, an LED module having features as described above canbe used in many applications such as, for example, indoor and outdoordecorative lighting, commercial lighting, spot lighting, and even roomlighting. With next reference to FIGS. 9–12, a self-contained lightingapparatus 100 incorporates an LED module 30 and can be used in many suchapplications. In the illustrated embodiment, the lighting apparatus 100is adapted to be installed on the side of a row of theater seats 102, asshown in FIG. 13, and is adapted to illuminate an aisle 104 next to thetheater seats 102.

The self-contained lighting apparatus 100 comprises a base plate 106, ahousing 108, and an LED module 30 arranged within the housing 108. Asshown in FIGS. 9, 10 and 13, the base plate 106 is preferablysubstantially circular and has a diameter of about 5.75 inches. The baseplate 106 is preferably formed of 1/16^(th) inch thick aluminum sheet.As described in more detail below, the plate functions as a heat sink toabsorb and dissipate heat from the LED module. As such, the base plate106 is preferably formed as large as is practicable, given aesthetic andinstallation concerns.

As discussed above, the lighting apparatus 100 is especially adapted tobe mounted on an end panel 110 of a row of theater chairs 102 in orderto illuminate an adjacent aisle 104. As shown in FIGS. 13 and 14, thebase plate 106 is preferably installed in a vertical orientation. Suchvertical orientation aids conductive heat transfer from the base plate106 to the environment.

The base plate 106 includes three holes 112 adapted to facilitatemounting. A ratcheting barb 116 (see FIG. 15) secures the plate 106 tothe panel 110. The barb 116 has an elongate main body 118 having aplurality of biased ribs 120 and terminating at a domed top 122.

To mount the apparatus on the end panel 110, a hole is first formed inthe end panel surface on which the apparatus is to be mounted. The baseplate holes 112 are aligned with mount surface holes and the barbs 116are inserted through the base plate 106 into the holes. The ribs 120prevent the barbs 116 from being drawn out of the holes once inserted.Thus, the apparatus is securely held in place and cannot be easilyremoved. The barbs 116 are especially advantageous because they enablethe device to be mounted on various surfaces. For example, the barbswill securely mount the illumination apparatus on wooden or fabricsurfaces.

With reference next to FIGS. 16–19, a mount tab 130 is provided as anintegral part of the base plate 106. The mounting tab 130 is adapted toreceive an LED module 30 mounted thereon. The tab 30 is preferablyplastically deformed along a hinge line 132 to an angle θ between about20–45° relative to the main body 134 of the base plate 106. Morepreferably, the mounting tab 130 is bent at an angle θ of about 33°. Theinclusion of the tab 130 as an integral part of the base plate 106facilitates heat transfer from the tab 130 to the main body 134 of thebase plate. It is to be understood that the angle θ of the tab 130relative to the base plate body 134 can be any desired angle asappropriate for the particular application of the lighting apparatus100.

A cut out portion 136 of the base plate 106 is provided surrounding themount tab 130. The cut out portion 136 provides space for components ofthe mount tab 130 to fit onto the base plate 106. Also, the cut outportion 136 helps define the shape of the mount tab 130. As discussedabove, the mount tab 130 is preferably plastically deformed along thehinge line 132. The length of the hinge line 132 is determined by theshape of the cut out portion 136 in that area. Also, a hole 138 ispreferably formed in the hinge line 132. The hole 138 furtherfacilitates plastic deformation along the hinge line 132.

Power for the light source assembly 100 is preferably provided through apower cord 78 that enters the apparatus 100 through a back side of thebase plate 106. The cord 78 preferably includes two 18 AWG conductorssurrounded by an insulating sheet. Preferably, the power supply is inthe low voltage range. For example, the power supply is preferably a12-volt alternating current power source. As depicted in FIG. 18, poweris preferably first provided through a full wave ridge rectifier 140which rectifies the alternating current in a manner known in the art sothat substantially all of the current range can be used by the LEDmodule 40. In the illustrated embodiment, the LEDs are preferably notelectrically connected to a current-limiting resistor. Thus, maximumlight output can be achieved. It is to be understood, however, thatresistors may be desirable in some embodiments to regulate current.Supply wires 142 extend from the rectifier 140 and provide rectifiedpower to the LED module 30 mounted on the mounting tab 130.

With reference again to FIGS. 9–12, 16 and 17, the housing 108 ispositioned on the base plate 106 and preferably encloses the wiringconnections in the light source assembly 100. The housing 108 ispreferably substantially semi-spherical in shape and has a notch 144formed on the bottom side. A cavity 146 is formed through the notch 144and allows visual access to the light source assembly 100. A secondcavity 148 is formed on the top side and preferably includes a plug 150which may, if desired, include a marking such as a row number. In anadditional embodiment, a portion of the light from the LED module 30, oreven from an alternative light source, may provide light to light up theaisle marker.

The housing 108 is preferably secured to the base plate 106 by a pair ofscrews 152. Preferably, the screws 152 extend through countersunk holes154 in the base plate 106. This enables the base plate 106 to besubstantially flat on the back side, allowing the plate to be mountedflush with the mount surface. As shown in FIG. 17, threaded screwreceiver posts 156 are formed within the housing 108 and are adapted toaccommodate the screw threads.

The LED module 30 is attached to the mount tab 130 by the pop rivets 72.The module 30 and rivets 72 conduct heat from the LEDs 32 to the mounttab 130. Since the tab 130 is integrally formed as a part of the baseplate 106, heat flows freely from the tab 130 to the main body 134 ofthe base plate. The base plate 106 has high heat conductance propertiesand a relatively large surface area, thus facilitating efficient heattransfer to the environment and allowing the base plate 106 to functionas a heat sink.

As discussed above, the first reflective strip 80 of the LED module 30is preferably bent so as to form a convex trough about the LEDs. Thesecond reflector strip 82 is attached to the base plate mount tab 130 ata point immediately adjacent the LED lamps 32. Thus, light from the LEDsis collimated and directed out of the bottom cavity 146 of the housing108, while minimizing the number of reflections the light must makebetween the reflectors (see FIG. 6). Such reflections may each reducethe intensity of light reflected.

A lens or shield 160 is provided and is adapted to be positioned betweenthe LEDs 32 and the environment outside of the housing cavity 108. Theshield 160 prevents direct access to the LEDs 32 and thus prevents harmthat may occur from vandalism or the like, but also transmits lightemitted by the light source 100.

FIG. 20 shows an embodiment of the shield 160 adapted for use in thepresent invention. As shown, the shield 160 is substantiallylenticularly shaped and has a notch 162 formed on either end thereof.With reference back to FIG. 18, the mounting tab 130 of the base plate106 also has a pair of notches 164 formed therein.

As shown in FIG. 16, the lens/shield notches 162 are adapted to fitwithin the tab notches 164 so that the shield 160 is held in place in asubstantially arcuate position. The shield thus, in effect, wraps aroundone side of the LEDs 32. When the shield 160 is wrapped around the LEDs32, the shield 160 contacts the first reflector film 80, deflecting thefilm 80 to further form the film in a convex arrangement. The shield 160is preferably formed of a clear polycarbonate material, but it is to beunderstood that the shield 160 may be formed of any clear or coloredtransmissive material as desired by the user.

The LED module 30 of the present invention can also be used inapplications using a plurality of such modules 30 to appropriately lighta lighting apparatus such as a channel illumination device. Channelillumination devices are frequently used for signage including bordersand lettering. In these devices, a wall structure outlines a desiredshape to be illuminated, with one or more channels defined between thewalls. A light source is mounted within the channel and a translucentdiffusing lens is usually arranged at the top edges of the walls so asto enclose the channel. In this manner, a desired shape can beilluminated in a desired color as defined by the color of the lens.

Typically, a gas-containing light source such as a neon light iscustom-shaped to fit within the channel. Although the diffusing lens isplaced over the light source, the light apparatus may still produce “hotspots,” which are portions of the sign that are visibly brighter thanother portions of the sign. Such hot spots result because the lightingapparatus shines directly at the lens, and the lens may have limitedlight-diffusing capability. Incandescent lamps may also be used toilluminate such a channel illumination apparatus; however, the hot spotproblem typically is even more pronounced with incandescent lights.

Both incandescent and gas-filled lights have relatively highmanufacturing and operation costs. For instance, gas-filled lightstypically require custom shaping and installation and therefore can bevery expensive to manufacture. Additionally, both incandescent andgas-filled lights have high power requirements.

With reference next to FIG. 21, an embodiment of a channel illuminationapparatus 170 is disclosed comprising a casing 172 in the shape of a“P.” The casing 172 includes a plurality of walls 174 and a bottom 176,which together define at least one channel. The surfaces of the walls174 and bottom 176 are diffusely-reflective, preferably being coatedwith a flat white coating. The walls 174 are preferably formed of adurable sturdy metal having relatively high heat conductivity. Aplurality of LED lighting modules 30 are mounted to the walls 174 of thecasing 172 in a spaced-apart manner. A translucent light-diffusing lens(not shown) is preferably disposed on a top edge 178 of the walls 174and encloses the channel.

With next reference to FIG. 22, the pop rivets 72 hold the LED module 30securely onto a heat conductive mount tab 180. The mount tab 180, inturn, may be connected, by rivets 182 or any other fastening means, tothe walls 174 of the channel apparatus as shown in FIG. 23. Preferably,the connection of the mount tab 180 to the walls 174 facilitates heattransfer from the tab 180 to the wall 174. The channel wall has arelatively large surface area, facilitating efficient heat transfer tothe environment and enabling the channel wall 174 to function as a heatsink.

In additional embodiments, the casing 172 may be constructed ofmaterials, such as certain plastics, that may not be capable offunctioning as heat sinks because of inferior heat conductanceproperties. In such embodiments, the LED module 30 can be connected toits own relatively large heat sink base plate, which is mounted to thewall of the casing. An example of such a heat sink plate in conjunctionwith an LED lighting module has been disclosed above with reference tothe self-contained lighting apparatus 100.

With continued reference to FIGS. 22 and 23, the LED modules 30 arepreferably electrically connected in parallel relative to other modules30 in the illumination apparatus 170. A power supply cord 184 preferablyenters through a wall 174 or bottom surface 176 of the casing 172 andpreferably comprises two 18 AWG main conductors 186. Short wires 188 areattached to the first and last contacts 62, 64 of each module 30 andpreferably connect with respective main conductors 186 using insulationdisplacement connectors (IDCs) 190 as shown in FIG. 23.

Although the LEDs 32 in the modules 30 are operated at currents higherthan typical LEDs, the power efficiency characteristic of LEDs isretained. For example, a typical channel light employing a neon-filledlight could be expected to use about 60 watts of power during operation.A corresponding channel illumination apparatus 170 using a plurality ofLED modules can be expected to use about 4.5 watts of power.

With reference again to FIG. 23, the LED modules 30 are preferablypositioned so that the LEDs 32 face generally downwardly, directinglight away from the lens. The light is preferably directed to thediffusely-reflective wall and bottom surfaces 174, 176 of the casing172. The hot spots associated with more direct forms of lighting, suchas typical incandescent and gas-filled bulb arrangements, are thusavoided.

The reflectors 80, 82 of the LED modules 30 aid in directing light raysemanating from the LEDs toward the diffusely-reflective surfaces. It isto be understood, however, that an LED module 30 not employingreflectors can also be appropriately used.

The relatively low profile of each LED module 30 facilitates theindirect method of lighting because substantially no shadow is createdby the module when it is positioned on the wall 174. A higher-profilelight module would cast a shadow on the lens, producing an undesirable,visibly darkened area. To minimize the potential of shadowing, it isdesired to space the modules 30 and accompanying power wires 186, 188 adistance of at least about ½ inch from the top edge 178 of the wall 174.More preferably, the modules 30 are spaced more than one inch from thetop 178 of the wall 174.

The small size and low profile of the LED modules 30 enables the modulesto be mounted at various places along the channel wall 174. Forinstance, with reference to FIGS. 21 and 24, light modules 30 mustsometimes be mounted to curving portions 192 of walls 174. The modules30 are preferably about 1 inch to 1½ inch long, including the mountingtab 180, and thus can be acceptably mounted to a curving wall 192. Asshown, the mounting tab 180 may be separated from the curving wall 192along a portion of its length, but the module is small enough that it issuitable for riveting to the wall.

In an additional embodiment shown in FIG. 25, the module 30 comprisesthe circuit board without the mount tab 180. In such an embodiment, thecircuit board 50 may be mounted directly to the wall, having an evenbetter fit relative to the curved surface 192 than the embodiment usinga mount tab. In still another embodiment, the LED module's main body 56is formed of a bendable material, which allows the module to fit moreclosely and easily to the curved wall surface.

Although the LED modules 30 disclosed above are mounted to the channelcasing wall 174 with rivets 182, it is to be understood that any methodof mounting may be acceptably used. With reference next to FIGS. 26A–C,an additional embodiment comprises an LED module 30 mounted to amounting tab 200 which comprises an elongate body portion 202 and a clipportion 204. The clip portion 204 is urged over the top edge 178 of thecasing wall 172, firmly holding the mounting tab 200 to the wall 174 asshown in FIG. 26B. The lens 206 preferably has a channel portion 208which is adapted to engage the top edge 178 of the casing wall 174 andcan be fit over the clip portion 204 of the mount tab 200 as shown inFIGS. 26B and 26C. This mounting arrangement is simple and providesample surface area contact between the casing wall 174 and the mountingtab 200 so that heat transfer is facilitated.

In the embodiment shown in FIG. 21, the casing walls 174 are about 3 to4 inches deep and the width of the channel is about 3 to 4 inchesbetween the walls. In an apparatus of this size, LED modules 30positioned on one side of the channel can provide sufficient lighting.The modules are preferably spaced about 5–6 inches apart. As may beanticipated, larger channel apparatus will likely require somewhatdifferent arrangements of LED modules, including employing more LEDmodules. For example, a channel illumination apparatus having a channelwidth of 1 to 2 feet may employ LED modules on both walls and may evenuse multiple rows of LED modules. Additionally, the orientation of eachof the modules may be varied in such a large channel illuminationapparatus. For instance, with reference to FIG. 26D, some of the LEDmodules may desirably be angled so as to direct light at various anglesrelative to the diffusely reflective surfaces.

In order to avoid creating hot spots, a direct light path from the LED32 to the lens 206 is preferably avoided. However, it is to beunderstood that pre-packaged LED lamps 32 having diffusely-reflectivelenses may advantageously be directed toward the channel letter lens206.

Using LED modules 30 to illuminate a channel illumination apparatus 170provides significant savings during manufacturing. For example, a numberof LED modules, along with appropriate wiring and hardware, can beincluded in a kit which allows a technician to easily assemble a lightby simply securing the modules in place along the wall of the casing andconnecting the wiring appropriately using the IDCs. Although rivet holesmay have to be drilled through the wall, there is no need for customshaping, as is required with gas-filled bulbs. Accordingly,manufacturing effort and costs are significantly reduced.

Individual LEDs emit generally monochromatic light. Thus, it ispreferable that an LED type be chosen which corresponds to the desiredillumination color. Additionally, the diffuser is preferably chosen tobe substantially the same color as the LEDs. Such an arrangementfacilitates desirable brightness and color results. It is also to beunderstood that the diffusely-reflective wall and bottom surfaces mayadvantageously be coated to match the desired illumination color.

Although this invention has been disclosed in the context of certainpreferred embodiments and examples, it will be understood by thoseskilled in the art that the present invention extends beyond thespecifically-disclosed embodiments to other alternative embodimentsand/or uses of the invention and obvious modifications and equivalentsthereof. In addition, while a number of variations of the invention havebeen shown and described in detail, other modifications, which arewithin the scope of this invention, will be readily apparent to those ofskill in the art based upon this disclosure. It is also contemplatedthat various combinations or subcombinations of the specific featuresand aspects of the embodiments may be made and still fall within thescope of the invention. Accordingly, it should be understood thatvarious features and aspects of the disclosed embodiments can becombined with or substituted for one another in order to form varyingmodes of the disclosed invention. Thus, it is intended that the scope ofthe present invention herein disclosed should not be limited by theparticular disclosed embodiments described above, but should bedetermined only by a fair reading of the claims that follow.

1. An illumination apparatus, comprising: a housing comprising a housingbody and a light-transmissive cover, the housing body and covercooperating to define an enclosed space, the housing body comprising aheat conductive base configured to function as a heat sink; a lightingmodule formed separately from the housing, the lighting modulecomprising: at least one light emitting diode (LED); a dielectric havingfirst and second sides; plural electrically-conductive contacts on thefirst side of the dielectric, the contacts being configured to mount theat least one LED such that the at least one LED is electricallyconnected to the contacts; and a heat conductive body connected to thesecond side of the dielectric; and a fastener; wherein the lightingmodule is adapted to be attachable by the fastener to the base withinthe enclosed housing space so that heat from the at least one LED flowsthrough the dielectric to the heat conductive body and to the base. 2.An illumination apparatus as in claim 1 additionally comprising a powerconditioner adapted to rectify an AC input power to a DC output powerand to deliver such conditioned power to the lighting module, whereinthe power conditioner is disposed adjacent the heat conductive base. 3.An illumination apparatus as in claim 2, wherein the power conditioneris enclosed in the space within the housing.
 4. An illuminationapparatus as in claim 1, wherein the fastener comprises an elongatefastener.
 5. An illumination apparatus as in claim 4, wherein the basecomprises an aperture adapted to accommodate the fastener in order toattach the lighting module on the base.
 6. An illumination apparatus asin claim 5, wherein the lighting module body comprises an apertureconfigured to accommodate the fastener.
 7. An illumination apparatus asin claim 6, wherein the fastener comprises a rivet.
 8. An illuminationapparatus as in claim 1, wherein the fastener comprises an adhesive. 9.An illumination apparatus as in claim 1, wherein the fastener comprisesa clip.
 10. A kit for making an illumination apparatus, comprising: apluraliti of lighting modules, each lighting module comprising: at leastone light emitting diode (LED); a dielectric having first and secondsides; plural electrically-conductive contacts on the first side of thedielectric, the contacts being configured to mount the at least one LEDsuch that the at least one LED is electrically connected to thecontacts; and a heat conductive body having a first face and a secondface, the first face connected to the second side of the dielectric andbeing in thermal communication with the plural contacts through thedielectric layer, the second face of the body having an engagementportion for thermally engaging a mount surface of an illuminationapparatus, the first face and the engagement portion of the second faceeach having a surface area at least the same as an aggregate surfacearea of one side of the contacts; wherein a fastening hole is formedthrough the heat conductive body and dielectric; and electricallyconductive members adapted to electrically connect the plurality ofmodules together.
 11. A kit as in claim 10 additionally comprising aplurality of elongate fasteners, each fastener adapted to fit through acorresponding fastening hole of a lighting module to secure the lightingmodule to an illumination apparatus with the engagement portion of thebody second face engaging a mount surface.
 12. A kit as in claim 11additionally comprising a power conditioner adapted to rectify an ACinput power to a DC output power and to deliver such conditioned powerto the lighting module.
 13. An illumination module for mounting on aheat conducting surface that is larger than the module, the modulecomprising: a heat conductive body having a first side and a secondside; a dielectric portion having first and second sides, the dielectricportion being arranged on the first side of the heat conductive body; alight emitting diode (LED); and a plurality of electrically-conductivecontacts on the first side of the dielectric portion, the contacts beingconfigured to mount the LED so that the LED is electrically connected tothe contacts; wherein a contact thermal communication area is defined asan aggregate surface area of one side of the contacts; and wherein thesecond side of the body has an engagement portion having a surface areaat least the same as the contact thermal communication area.
 14. Anillumination module as in claim 13, wherein the engagement area surfacearea is greater than the contact thermal communication area.
 15. Anillumination module as in claim 14, wherein a hole is formed through thebody and dielectric portion, the hole sized to accommodate an elongatefastener.
 16. An illumination module as in claim 14, wherein theengagement portion is generally planar.
 17. An illumination module as inclaim 16, wherein the engagement area comprises substantially the entiresecond side of the body.
 18. An illumination module as in claim 13,wherein the body is generally solid and has a volume greater than anaggregate volume of the plural contacts.
 19. An illumination module asin claim 13 in combination with a thermally- conductive base having amount portion, the mount portion integrally formed with the base,wherein the engagement portion of the body is attached to the mountportion of the base, and the base has a surface area greater than asurface area of the engagement portion.
 20. An illumination module as inclaim 19, wherein the engagement portion fits generally flush againstthe mount portion.